<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>
<body>

</body>
<script>
  function getSum(x, y) {
    console.log(x + y);
  }

  getSum(1,3);
  getSum(1, 2, 3);
  getSum(1);
</script>
</html>